JPH05203560A - Method for measuring distribution of concrete pore and method for judging deterioration of concrete member - Google Patents

Abstract

PURPOSE:To obtain a method for measuring the distribution of concrete pares which can provide an accurate distribution of pores through easy measurement of fine pores and make a safe and low-cost measurement work and a method for judging the deterioration of a concrete member which can be executed low-costly and rapidly. CONSTITUTION:A concrete member is cooled down, and AE (acoustic emission) generated by freezing moisture of pores present in the concrete is measured, so that a distribution of concrete pores is estimated from the correlation between its count and cooling temperature. A concrete member of predetermined blending is cooled down, and AE is measured to determine the correlation between its count and cooling temperature, where this correlation is compared with a predetermined reference correlation with the result that a deterioration situation of the concrete member is judged from the difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a pore size distribution of concrete and a method for determining deterioration of a concrete member, and particularly to acoustic emission (hereinafter referred to as AE).
The method for determining the concrete pore size distribution and the method for determining deterioration of a concrete member, which are obtained by measuring

[0002]

2. Description of the Related Art Conventionally, the pore size distribution of concrete has been used as an index for determining deterioration due to freezing and thawing of concrete members and estimating drying shrinkage. The pore size distribution indicates, for example, the distribution of fine pores existing in concrete, and, for example, the correlation between the pore size and the ratio of the total volume of pores of each diameter in a concrete of a predetermined size. Indicated by.

The measurement of the pore size distribution is generally carried out by the mercury intrusion method. That is, in this mercury injection method, mercury is pressed by a mercury porosimeter into a sample with a particle size of about 5 mm to 10 mm, which is obtained by cutting out a concrete member, and the pore size that can be pressed is determined by the pressure, and the amount of injection is determined. The volume for each pore size is obtained by.

On the other hand, as a method for determining the deterioration of a concrete member due to freezing and thawing, conventionally, a test method for examining the deterioration by rapidly repeating freezing and thawing has been generally employed. In this test method, a concrete sample is subjected to a freeze-thaw cycle of about -18 ° C to about -5.
300 degrees Celsius is performed for one cycle for 2 to 4 hours, and flexural vibration is measured for each predetermined cycle during that period to calculate a dynamic elastic modulus ratio, thereby evaluating durability of the concrete member.

[0005]

However, in the above-mentioned conventional method of measuring the pore size distribution of concrete by the mercury injection method, a high pressure is applied to the concrete sample at the time of injection of mercury, and the details thereof are destroyed. Therefore, there is a problem that it is difficult to measure pores having a very small diameter. Also, if the pores are constricted in the middle,
Even if the depth is wide, it is observed as a small diameter, so the measurement result is inaccurate. Further, since a sample having a small size is used, there is a problem in that data is dispersed due to dispersion of sampling points in the concrete member. Furthermore, since mercury is used, its treatment method is not easy to handle,
There is also a problem that the measurement cost becomes expensive.

On the other hand, the above-mentioned conventional method for judging deterioration of a concrete member has a problem that it takes a long time of about several months to carry out the test and the cost thereof becomes expensive. Further, although this can be determined for a specimen having a predetermined composition, there is a problem that it is difficult to determine the deterioration status of an actual structure outdoors.

Therefore, the present invention has been made to solve the above-mentioned problems, and it is possible to easily measure even fine pores and obtain accurate measurement results.
Furthermore, it is intended to provide a method for measuring the pore size distribution of concrete, which can be measured safely and inexpensively without using dangerous substances.

The present invention also provides a method for judging deterioration of a concrete member, which can be carried out in a short period of time at low cost and can easily judge the deterioration situation of an actual structure. To do.

[0009]

The present invention has been made in view of the above objects, and its gist is to measure an AE generated by cooling a concrete member and freezing water in pores existing in the concrete. Then, the method for measuring the concrete pore size distribution estimates the pore size distribution from the correlation between the count number and the cooling temperature.

Another aspect of the present invention is to cool a concrete member having a predetermined composition, measure AE caused by freezing of water in pores existing in concrete, and correlate the count number with the cooling temperature. The relationship is determined, the correlation is compared with a reference correlation between the AE count and the cooling temperature, which is measured in advance for a concrete member having a similar mixture or estimated from the predetermined mixture, and the concrete member is determined from the difference. This is a method for determining the deterioration of concrete members for estimating the deterioration.

The present invention will be described in more detail below.

The method for measuring the pore size distribution of the present invention comprises cooling a concrete member, measuring the AE produced by freezing of water in the pores existing in the concrete, and determining the correlation between the count number and the cooling temperature. Estimate concrete pore size distribution.

In the method for measuring the pore size distribution of concrete according to the present invention, as the concrete member to be cooled, for example, the water-cement ratio, the unit water amount, the air amount, etc., have been determined, and the mixing ratio has been determined. It is preferable to use concrete specimens.

The AE measured according to the present invention is a weak ultrasonic wave in which energy released due to deformation and destruction of a solid propagates as an acoustic pulse, and this AE is
For example, it is detected by a dedicated AE sensor for detecting this. Further, the AE caused by freezing of water in the pores means an AE generated by micro-deformation or micro-destruction of the surrounding concrete due to stress applied to the surrounding concrete when the water freezes to increase its volume. The state of pore distribution is analyzed by counting, that is, accumulating.

As for the water content in the pores, the smaller the pore size, the lower the freezing temperature of the condensate inside the pores.
Since the pore size can be calculated from the freezing temperature by a predetermined calculation formula, the distribution of the pore size can be estimated by obtaining the AE count number for each cooling temperature.

In the present invention, it is preferable to detect even fine pores and lower the temperature of the concrete member to about -70 ° C. so that an appropriate pore diameter distribution can be obtained.

The method for judging deterioration of a concrete member according to the present invention is characterized in that a concrete member having a predetermined composition is cooled and water A in the pores existing in the concrete is frozen.
E is measured, the correlation between the count number and the cooling temperature is obtained, and this correlation is predicted in advance for a concrete member having a similar mixture or is estimated from the predetermined mixture with the AE count number and the cooling temperature. The deterioration of the concrete member is estimated from the difference between the reference correlation and the reference correlation.

Here, in the method for judging deterioration of concrete of the present invention, as concrete members, concrete deterioration of concrete concrete specimens having a predetermined composition and, for example, actual concrete structures located outdoors are directly judged. You can also do it.

In the present invention, the measurement of AE caused by freezing of water in the pores and the analysis of the correlation between the count number and the cooling temperature are carried out according to the above method. In addition, in such a deterioration determination method for concrete, it is not always necessary to lower the cooling temperature of the concrete member to −70 ° C., and it is possible to determine the deterioration temperature, for example, near the minimum temperature that the actual concrete structure experiences depending on the surrounding environment. If cooling is possible, it is possible to easily determine the deterioration status of the concrete member based on the difference in the correlation within that range.

Furthermore, the reference correlation measured in advance is
Prior to the measurement of the concrete member whose deterioration should be judged, the concrete member having the same composition as this, for example, the concrete specimen, was cooled and the AE at the time of freezing was measured, and It refers to the correlation with the cooling temperature. On the other hand, the standard correlation estimated from the prescribed mixture is calculated from only the mixture of concrete according to various calculation formulas without actually cooling the concrete member, because the pore size distribution is mainly specified by the mixture of concrete members. It refers to the correlation between the counted number of AEs and the cooling temperature.

The deterioration status of the concrete member is
For example, it is determined whether the correlation between the AE count number and the cooling temperature has moved to the higher temperature side with respect to the reference correlation. That is, deterioration of a concrete member is represented by an increase in the number of large-diameter pores, and an increase in the number of AE counts at high temperature indicates an increase in the number of large-diameter pores. The deterioration of the member is determined.

[0022]

EXAMPLES Next, the present invention will be described in Examples 1 and 2 and Comparative Example 1,
2, but the present invention is not limited thereto.

[0023]

Example 1 As shown in FIGS. 1A and 1B, 48
Epoxy resin 11 is applied to a 10 cm × 10 cm × 40 cm concrete specimen 10 cured in water for about an hour to prevent drying, and an AE sensor 12 is attached to the surface of the epoxy resin 11. In addition, concrete specimen 10 and AE sensor 1
Silicon grease 13 is attached between the two and the AE sensor 12 and the concrete specimen 10 are fixed by a rubber ring 14 so that they are in close contact with each other. Then, the temperature of the concrete test piece 10 was lowered to about −70 ° C. for one cycle at a rate of 1 ° C./h, and the AE count number during that period was measured. 1
FIG. 2 shows the correlation between the AE count and the cooling temperature, which was obtained by measuring the AE during cycling and 100 cycles.
Shown in.

[0024]

[Comparative Example 1] FIG. 3 shows the distribution of pore diameters obtained by the mercury injection method for the sample collected from the concrete specimen 10 used in Example 1.

Comparison between Example 1 of FIG. 2 and Comparative Example 1 of FIG. 3 reveals that the shapes of the irregularities are similar, and the shapes of the irregularities change in the same manner as the number of cycles increases. It turns out that there is a correspondence. In addition, the shape of the unevenness is different in detail, when the pores are constricted in the middle,
It is presumed that this is due to an error due to the mercury injection method, such as the fact that even if the depth is wide, it is observed as a small diameter.

[0026]

[Embodiment 2] As shown in FIGS. 1 (a) and 1 (b), in the same manner as in Embodiment 1, 10 cm was cured in water for about 48 hours.
Epoxy resin 11 was applied to a concrete specimen 10 of × 10 cm × 40 cm to prevent it from drying, and
E sensor 12 is attached, and silicon grease 1 is placed between the concrete specimen 10 and the AE sensor 12.
3 is attached, and the AE sensor 12 and the concrete specimen 1
It is fixed by the rubber ring 14 so as to be in close contact with 0. When measuring the AE count for an actual structure, use the silicon grease 13, the rubber ring 14, etc.
The E sensor 12 can be easily attached. Then, the temperature of the concrete specimen was lowered to -40 ° C (outside air temperature of the actual structure) at a rate of 1 to 2 ° C / h, and the AE count number during that time was measured. When the temperature reached about -40 ° C, the temperature was raised to change from freezing to thawing, and the cycle was repeated 2-3 times (the actual structure was 2-3 months). FIG. 4 shows the correlation between the AE count and the cooling temperature obtained for the concrete specimens of good quality that are not deteriorated and the concrete specimens of deteriorated and poor quality.

[0027]

[Comparative Example 2] FIG. 5 shows the distribution of pore diameters obtained by mercury porosimetry for samples taken from concrete specimens of good quality and deteriorated concrete specimens used in Example 2. Shown in.

Comparing the example 2 of FIG. 4 with the comparative example 2 of FIG. 5, those with poor quality have an increased number of counts in a high temperature region near 0 ° C., and a high temperature region of this count number. The increase in (4) is an appropriate indication of the increase in the number of large pores, that is, the deterioration status of the concrete member. Therefore, in the curve showing the correlation between the AE count number and the cooling temperature in FIG. 4, the curve of the concrete member whose deterioration is to be determined is 0 ° C., in contrast to the curve of the concrete specimen of good quality which is the reference. By detecting that the concrete member has moved to the higher temperature side, it is possible to easily and quickly determine the deterioration state of the concrete member.

[0029]

INDUSTRIAL APPLICABILITY As described above, the method for measuring the pore size distribution of concrete according to the present invention measures the AE generated by cooling the concrete member and freezing the water in the pores existing in the concrete, and counting it. Since the pore size distribution is estimated from the correlation between the cooling temperature and the cooling temperature, it is possible to easily measure even minute pores by detecting ultrasonic waves caused by minute deformation or destruction of concrete members, and obtain an accurate pore size distribution. In addition, the measurement work can be performed safely and inexpensively without using a dangerous substance.

Further, the method for judging deterioration of a concrete member of the present invention measures the AE due to freezing while cooling the concrete member whose deterioration is to be judged and obtains the correlation between the count number and the cooling temperature, which is used as a standard. Since the deterioration status of the concrete member is estimated by comparison with the correlation, it is possible to determine the deterioration status inexpensively and quickly,
It is possible to easily determine the deterioration state of an actual uncured structure.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a situation in which AE is measured by a Kunclet test piece in Examples 1 and 2, (a) is a perspective view, and (b) is a side view.

2 is a chart showing measurement results according to Example 1. FIG.

FIG. 3 is a chart showing measurement results according to Comparative Example 1.

FIG. 4 is a chart showing the measurement results according to Example 2.

5 is a chart showing measurement results according to Comparative Example 2. FIG.

[Explanation of symbols]

 10 Concrete specimen 12 AE sensor

Claims (2)

[Claims] 1. A concrete member is cooled, AE (acoustic emission) generated by freezing of water in pores existing in concrete is measured, and a pore size distribution is calculated from a correlation between the count number and cooling temperature. A method for measuring the pore size distribution of concrete, characterized by estimating. 2. A concrete member having a predetermined composition is cooled,
AE (Acoustic Emission) caused by freezing of water in pores existing in concrete is measured, the correlation between the count number and the cooling temperature is obtained, and the correlation is calculated for a concrete member having the same mixture. Measured in advance or estimated from the predetermined composition,
A deterioration determination method for a concrete member, comprising comparing a reference correlation between an AE count and a cooling temperature and estimating the deterioration state of concrete from the difference.